by 5.0stang
 P: 63 I notice consistently in the aftermarket exhaust world that in the majority of cases, when a longtube is placed on an engine the low to mid-range power picks up. This is also with the same size diameter primaries but different lengths. So I am comparing: Long tube: 30" primary tubes into a 7-10" collector before going into mid-pipe. Short tube: 10-12" primary tubes into a 1-2" collector before going into mid-pipe. Why do longer exhaust primary tubes create more torque and low-mid range power?
P: 1
 Quote by 5.0stang I notice consistently in the aftermarket exhaust world that in the majority of cases, when a longtube is placed on an engine the low to mid-range power picks up. This is also with the same size diameter primaries but different lengths. So I am comparing: Long tube: 30" primary tubes into a 7-10" collector before going into mid-pipe. Short tube: 10-12" primary tubes into a 1-2" collector before going into mid-pipe. Why do longer exhaust primary tubes create more torque and low-mid range power?
Do the long tube headers you are reffering to remove the catalytic convertors?
 PF Gold P: 7,363 5.0stang, you keep asking questions related to exhaust scavenging, which is a very complex field. One of the things that impacts on exhaust scavenging is the duration of the exhaust pulse, which is inversely proportional to engine RPM. If you have relatively long primaries, the exhaust pulses are less likely to interfere at low RPM at the collector and more likely to assist in the evacuation of the other primaries, increasing efficiency. The easier your engine can "exhale" the more fuel-air mix it can process and the more horsepower it can produce.
 P: 63 Long tube headers vs. short tube headers. I asked this question back in January, but I do not mind that it was brought back-up. I just purchased Gordon Blair's book (D&S of a 4-stroke engine), and it goes into a lot of detail, that is hard for me to pick-up. You guys put it in easier terms for me to understand. David - Yes, the "cats" are removed. Thank you thus far!
 Sci Advisor PF Gold P: 1,474 Some pretty good advice above...if you still are undecided about which way to go...please post answers to following: How big (CID) is the engine? is it 4 cylinder? 6? V8? manual trans or automatic? what car is it in? what manufactured? is it singe or dual plane intake manifold stock cam or aftermarket? what type accessories ?/ air conditioning? power brakes? is it for daily driver , weekend racer or full race? remember, engineers have spent huge  and time to design a BALANCED intake/exhaust system and you are going to make significant changes to this design..you already removed the cat converter which will mess with the computer..if equipped... when you go to aftermarket headers I can tell you three things for a fact 1. it will be a lot louder in the cockpit 2. unless you go to stainless steel,,they will rust 3. you will replace header gaskets frequently